In the context of controlling combustion engines, sensors that indicate a position of the engine are used. It is usual, for example, by way of an encoder wheel installed fixedly with the crankshaft, to cause signals to be generated by a sensor at specific angles whenever a marking begins or ends. One or more markings on the encoder wheel are usually omitted so that a synchronization with the present engine position can be performed.
German Patent Application No. DE 100 637 55 A1 describes how a synchronization with a current engine position can be performed, one or more markings on the encoder wheel usually being omitted. Because the marking positions reproduce the present engine position only very coarsely, however, an angle base is generated with which, by way of an accurately defined number of pulses between two sensor signals, intermediate positions can also be determined. It is necessary for this, inter glia, to predict the time span until the next sensor signal.
German Patent Application No. DE 10 2005 047 922 A1 describes a method for determining an angle difference between a first and a second angle event. In the method, tooth times of preceding teeth are ascertained and successively added up to a spacing in time, the tooth angle being added to the difference angle, and the tooth times being ascertained from the tooth times of a preceding working cycle, multiplied by a correction factor.
Various kinds of errors can occur in the transfer of position signals and angle signals. Systematic errors in the transfer of angle data by way of an encoder wheel in a combustion engine can arise, for example, from the fact that teeth of the encoder wheel are broken off, or that the spacing between said teeth is not identical or appears to be non-identical. “Appears to be non-identical” is understood to mean, for example, that two teeth are missing, and that while the gap may be exactly three times as large as the spacing without the gap, signal sensing and transfer nevertheless does not reflect that exact ratio because of distortions. Such conditions have hitherto been taken into account only an approach involving exclusively software.